A memory device can be an integrated circuit (also known as a chip or a microchip) that includes numerous memory cells. When the size of a cell reaches nanometer scale, errors become essentially unavoidable. The errors can include permanent errors or soft errors. The permanent errors can be caused by defects. The defects can be quickly and consistently screened during testing. The defects can be replaced by good memory elements using standard memory redundancy technology.
The errors in memory systems can include soft errors caused by ionizing radiation, voltage glitches, pattern sensitive bits, or read/write error probability of memory bits. The errors can be caused by unreliable data paths between the memory bits and the read sensing circuits or write driver circuits. In the case of dynamic random access memory (DRAM) and statistic random access memory (SRAM) technologies, soft errors caused by ionizing particles can cause single bit error events, which oftentimes cannot be screened by normal testing. In the case of magnetic random access memory (MRAM) technology, including spin-transfer torque random access memory (STT-RAM) technology, the write and read error rates of each memory bit may be high enough where one in 1.0e9 events may be erroneous.